You know this whole idea about smartphones and tablets at the office might be going places when you see IBM showing interest in it.

Big Blue took a serious plunge into the mobile business today by teaming up with AT&T, launching new services for its clients and making it easier for its customers to develop software for mobile platforms. The initiative has been dubbed MobileFirst, and brings what IBM does best, including analytics, application development and cloud services, into a batch of services that make it easier for customers manage and secure the devices that employees use on the job, and to more easily develop applications they use to reach out to their own customers.

It’s a strong signal about IBM’s priorities going forward that, among other things, could indicate a preference for making acquisitions of companies in the mobile space in the future: It has already bought 10 mobile companies in the last four years. Prior strategic bets like this include Web commerce and data analytics. It’s also something IBM has been quietly doing for some time: It said it has already helped 1,000 companies get their mobile act together.

As for AT&T, the two are now partners on the mobile software development front. AT&T uses IBM’s Worklight mobile application development platform — Worklight was one of those 10 mobile acquisitions — to access AT&T APIs in the cloud, speeding up development of apps. Expect IBM to say more about this at the Mobile World Congress in Barcelona next week.